The woman, Dawn Nguyen, 24, was charged with knowingly making a false statement in the purchase of guns used in the slayings, U.S. Attorney William Hochul told a news conference Friday. She was charged earlier on a state violation of filing a falsified business record.

Hochul said Nguyen bought the guns on behalf of William Spengler, 62, who shot four firefighters responding to a fire he had started in his home on Monday outside Rochester, N.Y., killing two of them, before killing himself.

Nguyen "told the seller of these guns, Gander Mountain in Henrietta, that she was to be the true owner and buyer of the guns instead of William Spengler," he said. "It is absolutely against federal law to provide any materially false information related to the acquisition of firearms."

The complaint alleges that Nguyen acted as a "straw purchaser" for Spengler, who, as a convicted felon, could not legally own, acquire or purchase any firearm, Hochul said. The charges are related to an AR-15-type semiautomatic rifle and a 12-gauge shotgun — two of the three weapons found near Spengler's body Monday, according to State Police Investigator James Sewell.

Hochul said that a suicide note left by Spengler "includes information about obtaining the guns" from Nguyen.

WHEC

Police officers escort Dawn Nguyen on Friday.

The third weapon, a .38-caliber revolver, was not connected to Nguyen, Sewell said.

Nguyen's lawyer, Dave Palmiere, told the newspaper that Nguyen bought the weapons legally and that they had been stolen. He said Nguyen didn't recall whether she reported the guns stolen.

Monroe County Sherif's Dept. / EPA

William Spengler, in a 2006 photo, who authorities say set a house and car on fire on Christmas eve in Webster, N.Y. and then shot and killed two firefighters, and wounded two others who responded to the blaze.

Welsher told the Democrat and Chronicle that neither she nor her daughter, Nguyen, gave or sold Spengler the weapons.

"This is nuts," she said, according to the newspaper. "I never supplied this man with nothing. My daughter never supplied him with anything. He's setting us up."

The federal charge carries a maximum penalty of ten years in prison and a $250,000 fine, The Associated Press reported.

Spengler spent 17 years in prison for killing his grandmother in 1980.

After Monday's attack, a body was also discovered in Spengler's burned home. Investigators have said they believe the remains are those of his sister, Cheryl Spengler, 67, who lived with him. In all, seven houses were destroyed in the blaze.